Originally Posted by
Thunderroad
Once you achieve sufficient status, that in turn qualifies you for lounge access on international trips regardless of what class you travel in. In fact, one very nice perk of the AA program (that UA and DL do not share) is that upon achieving Executive Platinum status (basically, 100K miles per year), for international travel you get access to AA and its partners' first class lounges even when traveling economy. For instance, AA partners CX and BA have some very nice F lounges in its HKG and LHR hubs (though CX regular lounges in particular are not too shabby at all).
In addition to the lounge benefit with AA(which is a big one if you are traveling internationally) OW also gives free exit row / extra leg room seats as an EXP/OWE.
This includes CX which says on their website "The Marco Polo Club Diamond, Gold and Silver, or
oneworldŽ Ruby, Sapphire and Emerald members may reserve an Extra Legroom Seat free of charge." I believe this is also true with JL - though their US website is down so I can't find something definitive to post.
That would give you MCE/Extra Leg Room for free on all 3 potential TPAC carriers (AA, JL, and CX). I'm not sure if the other 2 alliances provide such an option (I don't recall receiving this benefit on other *A airlines back when I was UA 1K/Plat/*G) and can't speak to it at all with DL.
ex-NYC JL and CX would provide direct connects to NRT/HKG and onwards while AA would necessitate a transfer in ORD/DFW/LAX.